Contamination of the earth by organic contaminants is a major concern due to the possible environmental, health and financial problems relating to such contamination. Possible contaminants include a variety of organic materials such as crude petroleum, fossil fuels, lubricating oils and greases, solvents and others. It is economically and socially desirable to be able to identify contaminated sites so that potential risks can be evaluated and remedial action can be properly planned and pursued.
Sophisticated laboratory techniques are available to measure the presence and level of contaminants in earth samples. One such technique is to evaluate contaminants using chromatography. Sophisticated laboratory techniques, however, are expensive and are, therefore, typically impractical for use in large site surveys that require many tests to be performed in a systematic manner. They are also not well suited for use in the field. It is, therefore, desirable to have a testing technique which could be easily and inexpensively used in the field to identify contaminated sites. Once identified, then more elaborate laboratory tests could be performed to identify specific contaminants and to assist in planning for remediation, if necessary.
Several field testing techniques have been proposed in which a soil sample is extracted with a solvent to remove organic contaminants. The extract phase is then analyzed to gain information concerning the presence of contaminants and/or the level of contamination. One technique that has been used extensively for field testing involves the use of infrared spectroscopy to measure carbon-hydrogen bond stretch and uses a chlorofluorocarbon solvent. Chlorofluorocarbon solvents, however, pose serious environmental problems and their use is being severely restricted. Another technique involves indirect measurement for the presence of contaminants by looking for a color change in the extract phase caused by the presence of a Friedel-Crafts reaction in the presence of a Friedel-Crafts catalyst. That technique, however, uses an alkyl halide as a solvent, such as carbon tetrachloride, a known carcinogen. This technique, therefore, involves a serious health hazard. To reduce environmental and health risks, it would be desirable to avoid the use of halogenated organic solvents such as chlorofluorocarbons and carbon tetrachloride.
One technique that has been proposed involves an immunoassay and uses methanol as a solvent. The presence of contaminants is measured indirectly in an extract phase by observing color changes related to the activity of a biological agent that is added to the extract phase. Like the method using a Friedel-Crafts reaction, however, the immunoassay technique provides only an indirect indication of the presence of contaminants. The use of an indirect measurement, however, complicates testing and provides an additional opportunity for making a measurement error. Additionally, because of the use of a biological agent, the immunoassay technique is useful only over a narrow temperature range and the test kits have a very short shelf life. These limitations seriously limit the utility of the immunoassay technique in many field operations.
Based on the significant economic, health and environmental interests in identifying contaminated sites, it would be advantageous to provide a field testing procedure that is relatively inexpensive, reliable and safe and that is well suited for the variety of conditions that may be experienced during field testing.